You don't HAVE to use a snappi with a prefold (although I find that if your baby is exclusively breastfed, you will get poo on the cover often without a snappi). You can just fold it in thirds and lay it in the cover.

Any cover can go over a prefold or flat. You should decide if you want snaps or velcro, and if you want a one-size fits all or a sized diaper.

YES. You seem to have the idea. I stuff our pockets with flats and prefolds because I find them more absorbent and easier to clean. For DC, pre-stuffed pockets would be a great option. You could even use the pockets at DC and prefolds and covers at home if you want. I like having options.

How many prefolds or flats would I need for a two month old? And where can I get them? I only have one cloth diaper store and all they sell are BG pockets and FLIP/Rumparooz covers. (They're not this knowledgeable either...They make it seem like BG pockets and FLIP covers/inserts are the only ways to cloth diaper.)